1. Technical Field
The present invention relates to a group-III nitride compound semiconductor light emitting element, a manufacturing method therefor and a semiconductor light emitting device. More specifically, the preset invention relates to a group-III nitride compound semiconductor light emitting element that is capable of improving light extraction efficiency, a manufacturing method therefor and a semiconductor light emitting device.
2. Related Art
The amount of light in a semiconductor light emitting element depends on the degree of emissions in an interior thereof and light extraction efficiency of light extracted to the outside from the semiconductor light emitting element. In a case where the light is directed from the semiconductor layer of large refractive index to the outside of small refractive index, light equal to or larger than a critical angle (θc) is totally reflected at an element interface (see, paragraph [0003] in JP-A-2009-38407). That is, light less than the critical angle (θc) is extracted to the outside from the semiconductor layer whereas light equal to or larger than the critical angle (θc) is not extracted to the outside from the semiconductor layer. For this reason, it is difficult to obtain a sufficient amount of light of the semiconductor light emitting element.
Therefore, in JP-A-2009-38407, the normal to the side surface of the semiconductor layer and the normal to the surface of the semiconductor layer are set to be greater than 90° but less than 180°, for example (see, paragraph [0013] in JP-A-2009-38407). That is, it is intended to increase the component of light that is less than a critical angle (θc) by changing an angle of the side surface of the semiconductor layer. As a result, it is expected that more light is easily transmitted to the outside from the side surface of the semiconductor layer (see, paragraph [0027] in JP-A-2009-38407).
In the case of JP-A-2009-38407, the amount of light extracted from the side surface of the semiconductor light emitting element is increased. However, the effect is limited. The reason is that light propagating to the side surface is limited to a portion thereof. Accordingly, in order to increase the amount of light to be extracted, it is desirable to extract the light that does not propagate to the side surface, from a place other than the side surface.
The present invention has bar made to solve the above-described problems of a prior art. That is, an object of the present invention is to provide a group-III nitride compound semiconductor light emitting element that is capable of improving light extraction efficiency of the light extracted from the on-axis direction, a manufacturing method therefor and a semiconductor light emitting device.